Australia's flag is also called the Commonwealth Blue Ensign. It has three main design elements on a deep blue background:

The British Union Jack flag is in the upper left corner - noting Australia's ties to Great Britain

The Southern Cross constellation (5 stars) is on the right side of the flag - the Southern Cross is a major navigational constellation in the Southern Hemisphere

The large, white, seven-pointed Commonwealth Star (also called the Star of Federation) - it is symbolic of the original states of Australia.

On January 1, 1901, this flag was was chosen from about 30,000 entries in a public contest. Annie Whistler Dorrington, Ivor Evans, Leslie John Hawkins, Egbert John Nuttal, and Perth and William Stevens were declared winners of the design contest. It was officially adopted as the Australian flag in 1953.